US2612753A - Constant speed pump and motor hydraulic transmission - Google Patents

Description

Oct. 7, 1952 .1. E. BEvlNs 2,612'753 CONSTANT SPEED PUMP AND MOTOR HYDRAULIC TRANSMISSION Filed Nov. fr, 1947 s sheets-sheet 1 INVENTOR n ATTO R N EY Oct. 7, 1952 J. E. BEvlNs 2,612,753

CONSTANT SPEED PUMP AND MOTOR HYDRAULIC TRANSMISSION Filed Nov. 7, 1947 5 Sheets-Sheet 2 INVENTOR '2 ml/E5 E. BEV/N5 BY M 1/ M ATTORNEY Oct. 7, 1952 .1. E. BE'vlNs 2,612,753

CONSTANT SPEED PUMP ANO MOTOR HYDRAULIC TRANSMISSION Filed Nov. '7, 1947 5 Sheets-,Sheet 3 ATTORNEY Oct. 7, 1952 .1. E. BEvlNs 2,612,753

CONSTANT SPEED PUMP AND MOTQR HYDRAULIC TRANSMISSION Filed NOV. 7, 1947 5 Sheets-Sheet 4 'IIIA INVENTOR ATTORN EY J. E. BEVINS Oct. 7, 195

CONSTANT SPEED PUMP AND MOTOR HYDRAULIC TRANSMISSION 5 Sheets-Sheet 5 Filed Nov. 7. 1947 INVENTOR jfl/7755 E @E V//v5 ATTORNEY Patented Det. 7, 1952 CFFICE CONSTANT SPEED PUMP AND MOTOR HYDRAULKC TRANSMISSION `llames Emil Bovins, Ramsey, N. J., vassigner to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application November 7, 1947, Serial No. 784,708

This invention relates to constant speed transmissions, and particularly to a transmission of the hydraulic pump and motor type driven at variable speed, as by an aircraft engine.

Former devices of such character have been unduly heavy, have not held up in operation, are subject to excessive wear and have other disadvantages not adapting them particularly well to aircraft service.

An object of the present invention is to provide a device of the above-indicated character which is lighter in weight, holds up in operation over longer periods of time, is subject to less wear and has other advantages over prior devices for comparable duty, rendering it an effective aircraft accessory.

Another object is to provide a constant speed drive, comprising hydraulic motor, pump and control units, which will hold a substantially constant output motor speed of a predetermined number of revolutions per minute, such as 6000i300 R.. P. M., over a given range of pump input speeds, such as 2100 to 9000 R. P. M., at a continuous horsepower rating, such as fty, at input speeds over a given range, as between 3600 and 9000 R. P. M.

Another object is to provide a drive as aforesaid having a speed characteristic such that two or more thereof are adapted for parallel operation to drive alternators, and to have the power divided within reasonable limits by a built-in linear droop mechanism providing a speed regulation within denite percentage limits, such as eight per cent droop from no load to one hundred and fty per cent load in the alternator.

Another object is to provide a transmission of the above-indicated character which is simple and durable in construction, economical to manufacture, and effective in its operation.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example.

In the drawings:

Figure 1 is a schematic diagram of a trans` mission embodying the invention, showing, in each of its pump and motor units, only `one of several pistons of the actual structure, there being actually fifteen pistons in each unit;

Figure 2 is a side view, generally in section, of a portion of the actual motor unit;

Figure 3 is a detail view of a tirnin'g valve sembly indicated in Figure l, taken at right 6 Claims. (Cl. 60-53) 2 angles thereto, there actually being two of such assemblies in the device;

Figure 4 is a sectional view of a detail of the actual structure corresponding to a View taken substantially along the line 4-4 of Figure l;

Figure 5 is a diagram showing, at the left, a fragment of La motor piston and cam; at the center, a portion of the timing valve assembly of Figure 3, and, at the right, a valve cam andanother portion of the timing valve of Figure 3, all as positioned in relation to each other at a certain phase or step of the motor operation, when duid flow to or from the motor piston is completely shut off;

Figure 6 shows the parts of Figure 5 as related at a next subsequent step of operation, when the motor piston is'fully subjected to the pressure fluid;

Figure 7 shows the parts of Figure 5 as related at a third successive step of operation, in

which the pressure and exhaust uids are again completely shut oir from themotor piston; and

Figure 8 shows the parts of Figure 5 as related at a fourth successive step of operation, in which the valve is fully open for discharge of fluid from the motor piston to a sump.

Referring to Figure l, an aircraft hydraulic transmission unit Il) comprises a housing I2 having a sump I4, an engine driven shaft I5 of a pump i8, and a shaft 20 of a uid motor 22 adapted to drive a generator.

Referring to Figure 2, since Figure 1 illustrates only one piston and associated parts in the pump i8, and only one piston and associated parts in the -fluid motor 22, the subsequent description should be read with the actual structure of the motor 22 of Figure 2 in mind, the latter figure also constituting, in effect, a showing of the pump lil, since the only substantial dilference between corresponding portions of the motor and the pump resides in the areas of the pump pistons which are larger than the areas of the motor pistons.

Eccentric cams 24 are fixed relative to the motor shaft 2li, Whereas eccentric cams 2t, only one of which is shown in Figure 1, are movably mounted on the pump shaft I6, and are adapted to vary the pump output with the pump and motor cams 26 and 24, respectively, each having segmental surface grooves 28, Figures 5-8, adapted to receive fluid from,.and'to discharge iiuid to, the sump I6, respectively. For purposes of clarity, only one cam 26 is shown in Figure 1, it being understood that the banks of pistons disposed on either side of pistons 36, shown in 'Figure 1 are each provided with a cam 2E.

Pump and motor blocks 30 and 32, respectively, each embodies an odd number of cylinder banks, in this case three, see Figure 2, offset along its shaft, with the cylinders 3| and 33 of the odd banks of the motor and pump, respectively, symmetrically offset from the cylinders 34 of the even bank or banks about its shaft, and having total cylinder area substantially equal to the total even bank cylinder area.

A fluid pressure collector 38 is indicated in Figure 1 as in the form of an annular circular section channel having outlets 39. The cylinders 3| and 34 of the motor 22 have inlets 42 from the collector 38, and the cylinders 33 of the pump |8 have outlets 46 to the collector 38, which outlets 46 are provided with ten poppet valves 48 controlling fluid flow from the pump to the collector 38.

Pump cam eccentricity varying means 50, associated with the pumpshaft I6, and to be further set forth, is adapted to be actuatedbymeans including a servo piston 54 aligned with the shafts I6 and 20.

The cylinders 3|, 33 and 34 enclose pistons 35,

36 and 31, respectively, each of the throughopens housing I2, as by vbolts 63, and having `radial cylinders 64 communicating with the collector outlets 39 and the motor inlets 42, as seen in Figures 1 and 5-8. Plungers 66 having lands 61 in the cylinders 64 arel biased, by springs 68, against a cam 10 eccentrically mounted on the shaft 20. The springs 68 are backed by washers 12 and lock rings 14, Figure 3.

Although only one radial valve means 60 is indicated inthe diagram of Figure 1, there are actually two of such means. Also, the plungers 66, instead of being maintained on the cam 10 by the springs 68 may be maintained as are the cam shoes 56 at Figure 2 wherein the shoes are maintained by rings 15, also indicated in Figure 1. The plungers 66 may also be maintained by fluid pressure.

Pump fluid operated control means 16, Figure 1, controlled by centrifugal means 18 responsive to the rate of rotation of the motor shaft `2|), is adapted to regulate the servo piston 54 in maintaining the pump output and the rate of rotation of the shaft 20 at substantially constant values between zero load and a given overload, as above mentioned, irrespective of variations in the speed of the pump shaft I6. The means 16 includes means 80 responsive to loads on the motor shaft 20 providing for a change in the motor shaft speed within definite percentage limits of the above-mentioned constant values.

The pump cam eccentricity varying means 50, see also Figure 4, comprises a square-section portion 82 of the pump shaft I6, having sliding fit in rectangular holes 84 of the pump cams 26. A rod 86, actuated by the servo piston 54 is axially slidable in the shaft portion 82 and carries a pin 92 slidably fitting a cam slot 94 in each of the cams 26.

Movement of the servo piston 54, right or left, as viewed in Figure 1, acts through the rod 86, the pins 92 and the axially sloping cam surfaces '4 defining the slots 94 to vary the radial distance between cam surfaces of the cams 26 and the axis of the shaft I6, thus varying the lengths of the strokes of the pump pistons.

A pair of ball bearings 96, Figure 1, are mounted between the rod 86, which rotates with the pump shaft I6, and the non-rotative servo piston 54, which is sealed by ring seals 98 and |00.

The pump shaft I6 is journaled, at opposite sides of its cams 26, in ball bearings |02, and provided near its outer end with a bellows seal |04. The motor shaft 20 is journaled, at opposite sides -of its cams 24, in ball bearings |06, and

provided near its outer end with a bellows seal |108.

'The vcentrifugal means 18, Figure 1, comprises ashaft I|0 journaled in bearings |I2 having a gear |'|4, Figure 1, adapted to engage and be rotated by a gear |I6, Figure 2, on the moto-l` shaft 20. A governor device I|8 comprises a support |20 fixed to the shaft |I0, to which support .are pivotally mounted, by pins |22, bell `crank weight levers I 24 held, when stationary, against astop |26, by a spring or springs |28.

When the shaft vI I0 rotates, portions |30 of the bell cranks |24, raise a rod |32 to cause a beam |34 of the means 16 to pivot about a pin |36 which is eccentrically adjustable about an axis |38 in a slot |44. To compensate for such adjustment, a screw |46 may be adjusted relative to a needle valve pin |48 which it depresses against the action of a spring |50 associated with a servo cylinder |54, relative to an orifice |56 in a servo pilot Aplunger |58. The orifice |56 leads into a chamber |51 containing a port |59 which communicates with the exterior of the servo cylinder |54. The pilot plunger |58 is slidable in a droop sleeve |60 over a spring |62 in the sleeve, and has ,lands |64 and |66, at opposite sides of a side duct |68 in the sleeve 60, and controls ducts |10 and |12, respectively, also in the sleeve |66. The duct |68 registers with a conduit |14, and theducts |10 and |12 communicate with conduits |16 and |18, respectively, leading to the left and right hand sides, respectively of the servo piston 54, as indicated in Figure 1. Droop sleeve |60 is also provided with a drain port |19 to permit exhausting of servomotor 54 when it moves to the right as shown in Figure 1.

The conduit |14 communicates with a reducing valve |80, comprising a casing |82, a sleeve |84, a spring |86, and a plunger |88, the casing |82 having an inlet |90 from the collector 38.

A droop valve y'|92 comprises a casing |94 connected to the inlet |90, and containing a plunger |96 biased upwardly, as shown, by a spring- |98 extending between the bottom of the casing |94 and a disc I 99. Two balls 200 operate as a non binding piston under the high pressures involved.

The plunger |96 and the droop sleeve |60 are connected by alink 202 having a slot 204 in which a pivot pin 206 is free to ride. The pin 206 is attached to a member 208 which in turn slidably mounted on the support 2|0 so that by sliding the member 208 along the support 2|0, the pin 206 may be adjusted in any desired position in slot 204.

In operation, on the intake stroke, hydraulic oil is drawn through the apertures 58 of the pump piston shoes 56 from the sump I 4, the latter being defined by the housing |2, which is filled with oil and held at inlet pressure of approximately ten to fifteen pounds per square inch.

On the compression stroke of each piston 36,

the poppet valves 48 are opened, when the pressure build up is greater than the vpressure in the collector 38, allowing the oil to flow into collector. Thus, there are fteen pump pistons 36 so displaced as to effect a relatively even flow of oil through the ten poppet valves d8 to v the collectori.

Since the speed of the motor 22 must bel substantially constant, the flow from they pump I8 must be correspondingly constant over a pump input speed range, in this instance, of fromg2000 to 9000 R. P. M. Substantially constant flow from the pump i8 is obtained by varying the I8 is accomplished by means of the control means 76 and the master servo 5d operating in conjunc-Y tion with the variable stroke pump cams 25.

An increase in the speed of the motor shaft acts through the gear H5, Figure 2; the gear i i4, Figure 1, the shaft I i0, the portions |30, the rod |32, the beam |36, and the screw |45 to cause a downward motion of the needle valve pin |68 which, in turn, starts to close the orificei. Since the conduit |74 communicates with the casing |32 which in turn has an inlet |99 frorn'the collector 3S, pressure is built up in the servo pilot cylinder |54 which moves the servo pilot |58v downwardly, allowing Qil under pressure to vfiow into the conduit |18 which communicates with the cylinder of the master servo piston 5i,`thus moving the piston 5d to the left and decreasing the stroke of the pump pistons 35 by moving the pins 32 such as to move the high points of the pump cams 26 closer to the axis of the pump shaft I6.

A decrease in the speed of the motor shaft 2li conversely allows the servo pilot 5t to move upwardly by spring 62, allowing oil under .pressure to flow into the conduit |16, thus moving the mas'- ter servo piston 54 to the right and increasing the stroke of the pump pistons.

To obtain the 8% droop, desired in this inf,

stance, over a load range of 0 to 150%, the niember 208, Fig-ure l, is adjusted along the support 210 to adjust the position of the pin 255 so that', at any point between 0 and 150% load, the speed of the motor 22 will correspond to a predetermined value determined from a speed-load curve incorporating the 8% droop. The relative positions of the droop sleeve |50 and the servo pilot G53 are set by the adjusting sliding pivot 205 `to give the required droop characteristics.

In the operation of the motor 22, hydraulic oil under pressure in the collector 38 is ported to the motor pistons 35 and 37 in proper sequence by the valve plungers t6 operated by the cam it on the motor shaft 20.

In Figure 5, the piston 35 is atthe ton of its Figure 6. This pressure on the piston exerts'al force tending to rotate the motor-shaftlinithe counterclockwise direction indicated by an arrow,

as shown.

In'Figure 6, the pistonf35 is shown as lposi-'- tioned after'the shaft 20 has rotated 90 from its position of Figure 5. Itis half way on the Idown stroke, Vwhereas'theA timing valve plunger 6G has reached its lowermost position. At this stage, the inlet port 42 to the cylinder of the piston 35 is wide'open, and the piston is undery the full pump outlet pressure of the oil from the outlet 39.'

`- The port 2te the piston 35 will be gradually closed-during the 'next following 90 rotation of the shaft 2li until, as in Figure "I, it is'completely closed again as' it is in Figure 5, the only difference being that the piston 35 is now at the bottom of the stroke andthe timing valve 66 again at half stroke. v During thenext subsequent 90 rotation of the shaft 20, theV port 42 will be gradually opened, but, this time, to the inlet side allowing, oil to be discharged through'the port e2 by'way of the plunger 'B6 to the sump. Oil is also discharged through the piston shoe by way of the groove 28 while the piston `35 is on'its up stroke.

At the position of Figure 8,`the piston is `half way'on yits up stroke and the timing valve 56 is at the `top of'its stroke, at which time the valve port 42 is wide open to the inlet side of the drive. During the next subsequent rotation, the valve 'port t2 is gradually closed, allowing oil to ow from the piston vto the inlet'side until the valve port 42 is completely closed, as in Figure 5.

Gil is also allowed to flow through the piston shoe by Way ofthe groove 28 to the inlet side until the piston shoe is over the solid section of the camfasindicated in Figure 5.

Although only one embodiment of the invention has been illustrated and described, various changes in` the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is: f

1,'InV an aircraft hydraulic transmission, the combination of a sump, 'an engine driven `pump shaft, a motorshaftto drive a generator, eccentric cams xed to the motor shaft, eccentric cams movable on the pump shaft to vary the pump output-the pumpand motor cams having segmental'cam surfacegrooves to receive fluidfrom and to discharge fluid to the sump,` respectively, Dump and motor blockseach embodying an odd number of cylinder banks oiset along its shaft with the cylinders of the odd banks symmetrically onset from the cylinders of the even bank or banks about its shaftv and having total cylinder area substantiallyequal' to the total even bank cylinder area, a pump output collector, the motor cylinders having inlets from the collector and the pump cylinders having outlets to the collector, poppet valve means controlling the delivery of the pump output to the collector, pump cam eccentricity varying means associated with' the pump shaft, means including a servo piston aligned with the shafts for actuating said eccen tricity varying means, a through opening tubular pistonv inv each cylinder including a. pivoted cam shoel havinga carn engaging surface aperture between its cylinder andcam, radial valve means to distribute' pump y' output from the collector to the motor cylinders, eccentric means on the motor shaft fcroperating said radial valve means, centrifugal means responsive to motor shaft speed;

pump pressure responsive means, and pump fluid operated valve means controlled by joint operation of said centrifugal and pump pressure responsive means to regulate the servo' piston in maintaining said pump outputI and said motor shaft speed `at substantially constant values between zero load and given overload irrespective of variations in the speed of; the pump s haftand providing for a change-in the motor shaft speed withinv definite percentage limits of said constant values.

2. In a. hydraulic transmission, the combination of a pump shaft, a motor shaft, eccentric cams fixed to the motor shaft, a sump, movable eccentric cams on lthe vpump shaft to vary the pump output, the pump-and motor -camslhaving segmental cam surface-grooves to receive fluid from and to discharge f'luid to the sump, respectively, pump and motor blocks each embodying an odd number of cylinder banks offset along its shaft with the cylinders of the odd banks symmetrically offset from the cylinder or cylinders of the even bank or banks about its shaft and having total cylinder area. substantially equal to the even bank total cylinder area,a pump output collector, the motor cylinders having inlets from the collector and the pump cylinders having outlets to the collector, valve means controlling delivery of the pump output -to the collector, pump cam eccentricity varying means, means including a servo piston to actuate said eccentricity varying means, a through opening tubular piston in each cylinder including a pivoted cam shoe having a cam engaging surface aperture between its cylinder and cams, radial valve means to distribute pump output from the collector to the motor cylinders, eccentric means on the motor shaft for operating said radial valve means, centrifugal means responsive to motor shaft speed, pump pressure responsive means and pump fiuid operated valve means controlled by the joint operation of said centrifugal and pump pressure responsive means to regulate the servo piston in maintaining said pump output and said motor shaft speed at substantially constant values between zero load and given overload irrespective of variations in the speed of the pump shaft and providing for a change in the motor shaft speed within definite percentage limits of said constant values.

3. In hydraulic transmission means, the comhaving segmental cam surface grooves to receive fluid from and to discharge fluid to the sump, respectively, pump and motor blocks each embodying an odd number of cylinder banks offset along its shaft with the cylinders of the odd banks symmetrically-offset from the cylinder or cylinders of the even bank or banks about its shaft and having total cylinder area substantially equal to the even bank total cylinder area, a pumpoutput collector, the motor cylinders having inlets from said collector and the pump cylinders having outlets to the collector, valve means controlling delivery of pump output from the pump to the collector, pump cam eccentricity varying means, servo means to actuate said eccentricity varying means, a through opening tubular piston in each cylinder including a pivoted cani shoe having a cam engaging surface aperture between its cylinder and cam, a valve device to distribute the pump output from the collector to the motor cylinders, means operating said valve device from the motor shaft, centrifugal means responsive to motor shaft speed, pump pressure responsive means, and pump fluid operated valve means controlled by the joint operation of said centrifugal and pump pressure responsive means to regulate said servo means in maintaining said pump output and said motor shaft speed at substantially constant values between zero load and given overload irrespective of variations in the speed of the pump-shaft.

4. In hydraulicl transmission mean-s, the combinatlon of a sump, a fluid operated motor including outlet means to the sump and having a shaft, a collector, a pump including a shaft and connected to pump fluid from the sump to the collector, means including valve means for controlling the delivery of pump output from the pump to the collector. means to vary the output of the pump, said vary means comprising a plurality of eccentric cams on the pump shaft rotative herewith and radially movable relative thereto, the pump shaft being hollow and having sloping slots to increase and decrease eccentricity of the cams, a rod axially movable in the pump shaft, and pins projecting laterally from the rod and disposed one extending through each of said sloping slots, a piston concentric with said pump shaft to move the rod axially, valve means distributing the pump output from the collector to the motor for actuating the motor, centrifugal means responsive to motor shaft speed, pump pressure responsive means, and valve means controlled by the joint operation of said centrifugal and pump pressure responsive means to actuate said piston and thereby said pump output varying means in maintaining said pump output and said motor shaft speed at substantially constant values between zero load and given overload irrespective of variations in the speed of the pump shaft.

5. In hydraulic transmission means, the combination of a sump, a fluid operated motor including outletvmeans to the sump and having a shaft, a collector, a pump including a shaft and connected to pump fiuid from the sump to the collector, means including valve means for controlling the delivery of pump output from the pump to the collector, means to vary the pump output, said varying means comprising a plurality of eccentric cams on the pump shaft rotative therewith and radially movable relative thereto, means including a rod axially movable in the pump shaft to move said cams radially, and piston means to move the rod axially, valve means distributing the pump output from the collector to the motor for actuating the motor, centrifugal means responsive to motor shaft speed, pump pressure responsive means, and valve means controlled by said centrifugal and pump pressure responsive means to actuate said piston means and thereby the pump output varying means in maintaining said pump output and said motor shaft speed at substantially constant values between zero load and given overload irrespective of variations in the speed of the pump shaft.

-6. In hydraulic transmission means, the combination of a sump, a fluid operated motor including outlet means to the sump and having a shaft, a collector, a pump including a shaft and connected to pump fluid from the sump to the co1- lector, means including valve means for controlling the delivery of the pump output from the pump to the collector, means including piston means to vary the out'put of the pump, radial valve means controlling the delivery of pump output from the collector to said motor for actuating the motor, radial valve actuating means including eccentric means carried by the motor shaft, centrifugal means responsive to motor shaft speed, pump pressure responsive means, and valve means controlled by joint operation of said cen- 9 trifugal and pump pressure responsive means to actuate said piston means and thereby the output varying means in maintaining said output and said motor shaft speed at substantially constant values between zero load and given overload irrespective of variations in the speed of the pump shaft.

JAMES EMIL BEVINS.

REFERENCES CITED The following references are lof record in the file of this patent:

Number l0 Number

Images